Method and system for luminance characterization

ABSTRACT

A system for luminance characterization of a luminaire includes a ballast coil and a multi-tap capacitor connected in series with the ballast coil. The multi-tap capacitor has a plurality of tap capacitors integrated into a capacitor housing. A plurality of switches are each coupled to one of the plurality of tap capacitors for selectively coupling the tap capacitors together to produce a multi-tap capacitance corresponding to a configuration of the plurality of switches. A lamp is connected in series with the multi-tap capacitor and the ballast coil. A photometer is located to measure light intensity of the lamp and to produce a lumen output measurement. A memory is used to store a database having a plurality of lumen output measurements, each corresponding to a multi-tap capacitance corresponding to all configurations of the plurality of switches.

RELATED APPLICATIONS

This application claims priority from Provisional Application Ser. No.60/695,459, filed on Jun. 30, 2005, and Provisional Application Ser. No.60/702,461, filed on Jul. 26, 2005, both of which are herebyincorporated herein in their entirety by reference. This application isrelated to co-pending U.S. patent applications Ser. No. 11/476,498,filed Jun. 28, 2006; Ser. No. 11/479,769 filed Jun. 30, 2006; and Ser.No. 11/479,222 filed Jun. 30, 2006, which applications are herebyincorporated herein in their entirety by reference.

FIELD OF THE INVENTION

This invention relates in general to the operation of light fixtures,which can include ballasted high intensity discharge (HID) luminaires,and more specifically to the control, adjustment, compensation, andmonitoring of the lumen output from a light fixture.

BACKGROUND OF THE INVENTION

As saving energy becomes more important, it has become desirable toreduce the energy consumption associated with widely used lightingsystems and light fixtures, which fixtures can include HID luminaires.At present roadways, highways and residential streets are fully litthroughout the night, despite lighter traffic use between midnight anddawn.

HID lamps, and their lamp fixtures or HID luminaires, are typically usedwhen a high level of light over a large area is required, and whenenergy efficiency and/or long life are desired. Uses that are wellsuited for such HID luminaries include gymnasiums, large public areas,warehouses, buildings, signs, outdoor activity areas, sports fields,roadways, parking lots, and pathways. More recently, however, HIDsources, especially metal halide, have been used in small retail andresidential environments. Conservative estimates suggest there are atleast 150 million HID luminaires worldwide on roadways alone.

HID lamps—which includes mercury vapor (MV) lamps, metal halide (MH)lamps, high-pressure sodium (HPS) lamps, low-pressure sodium lamps, andless common, xenon short-arc lamps-have light-producing elements thatuse a well-stabilized arc discharge contained within a refractoryenvelope (arc tube).

Light fixtures can have their lumen output adjusted to save energy whenfull brightness is not needed, such as when lighted areas are notoccupied, or during periods of reduced usage. Full brightness can berestored when increased occupancy is detected.

However, there are several problems and difficulties with adjusting andcontrolling the lumen output of HID lamps. One of the reasons for theproblems is that ballasts are required to start the lamp, to regulatethe lamp starting and lamp operating currents, and to sustain anappropriate supply voltage. A first problem is that HID lamps requireseveral minutes to ignite, warm-up, and reach their full light outputlevels. Second, HID lamps also have a hot re-strike problem, which makesthem difficult to re-ignite within a short period after being turnedoff, while they are still at an elevated temperature. Depending upon theballast-lamp combination, it can take up to 10 minutes after the lamphas been turned off before it can be re-ignited. This poses a practicalproblem for lamp adjustment applications involving pedestrian conflictor roadway safety where the lamp must be returned, within a very shortperiod of time (i.e. within milliseconds), to an acceptable level ofbrightness and illumination. If the HID lamp is turned off, it may takeseveral minutes after re-ignition until the lamp warms up sufficientlyto produce the desired output.

Several methods can be used for adjusting the lumen output, and thepower consumption, of ballasted HID luminaires. A first method uses avariable voltage transformer to reduce the primary voltage supplied tothe ballast, thereby achieving lumen adjustment to approximately 60% ofthe rated lamp power. Typically, in this type of arrangement, an HIDluminaire contains a lamp as well as some type of transformer ballastwith a series-connected inductance and capacitance (L-C circuit), in theform of a choke and capacitor, for controlling the lamp operatingcurrent according to the voltage-current characteristics specified forthe ballast-lamp combination.

A second method uses a variable reactor in the ballast circuit to changethe lamp current without affecting the voltage. This method allows awider range of lumen and power adjustment, permitting a reduction toapproximately 30% of rated power, depending upon the lamp and ballastcombination.

A third method for adjusting lumen output uses solid-state components tochange the waveforms of both the current and voltage input to theballast, which permits adjusting lumen output down to approximately 50%of rated power.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying figures, wherein like reference numerals refer toidentical or functionally similar elements throughout the separate viewsand which together with the detailed description below are incorporatedin and form part of the specification, serve to further illustratevarious embodiments and to explain various principles and advantages,all in accordance with the present invention.

FIG. 1 depicts, in a simplified and representative form, a high-levelblock diagram of a controller and multi-tap capacitor in a constantwattage isolated (CWI) configuration for controlling a luminaire inaccordance with one or more embodiments;

FIG. 2 illustrates, in a simplified and representative form, thecontroller and multi-tap capacitor of FIG. 1 in a constant wattageautotransformer (CWA) configuration for controlling a luminaire inaccordance with one or more embodiments;

FIG. 3 is a perspective view of a multi-tap capacitor in accordance withone or more embodiments;

FIG. 4 depicts a schematic circuit diagram of the multi-tap capacitor ofFIG. 3 in accordance with one or more embodiments;

FIG. 5 is a high-level flowchart of processes executed by a controllerthat can be used in conjunction with the FIG. 1 luminaire control systemin accordance with one or more embodiments;

FIG. 6 illustrates switch setting data that can be used by luminaire 100of FIG. 1 in accordance with one or more embodiments;

FIG. 7 depicts a log file stored in luminaire 100 of FIG. 1 inaccordance with one or more embodiments;

FIG. 8 depicts a lumen level schedule in accordance with one or moreembodiments;

FIG. 9 illustrates a portion of a database containing luminancecharacterization profiles in accordance with one or more embodiments;

FIG. 10 depicts a high-level flowchart of a process of creating aluminance characterization profile in accordance with one or moreembodiments; and

FIG. 11 shows a test station for creating a luminance characterizationprofile in accordance with one or more embodiments.

DETAILED DESCRIPTION

In overview, the present disclosure concerns controlling lumen outputand power consumption of light fixtures, including ballasted HID lamps.More specifically, various inventive concepts and principles embodied inmethods and apparatus can be used for controlling, adjusting,compensating, and monitoring operating parameters of a luminaire. Themethods and apparatus are particularly suited for ballast circuits thatemploy a capacitor, such as core and coil transformer ballastarrangements, which can be commonly referred to as Constant WattageAutotransformer (CWA) ballasts, and Constant Wattage Isolated (CWI)ballasts.

While the luminaire controller methods and systems of particularinterest may vary widely, one embodiment may advantageously be used inan overhead street light, which is commonly used to illuminate roadways,highways, and residential streets. Additionally, the inventive conceptsand principles taught herein can be advantageously applied to otherlighting systems, particularly where it is advantageous to control thelight level output, or lumen level output, of the luminaire, and whereit is advantageous to adjust, compensate, and monitor luminaire outputand power consumption of a light fixture or lighting system.

The instant disclosure is provided to further explain, in an enablingfashion, the best modes, at the time of the application, of making andusing various embodiments in accordance with the present invention. Thedisclosure is further offered to enhance an understanding andappreciation for the inventive principles and advantages thereof, ratherthan to limit the invention in any manner. The invention is definedsolely by the appended claims, including any amendments made during thependency of this application, and all equivalents of those claims asissued.

It is further understood that the use of relational terms, if any, suchas first and second, top and bottom, and the like, are used solely todistinguish one entity or action from another without necessarilyrequiring or implying any actual such relationship or order between suchentities or actions.

Much of the inventive functionality and many of the inventive principlescan be implemented with, or in, integrated circuits (ICs), possiblyincluding application specific ICs, or ICs with integrated processing,which can be controlled by embedded software, firmware, or program code.It is expected that one of ordinary skill-notwithstanding possiblysignificant effort and many design choices motivated by, for example,available time, current technology, and economic considerations-whenguided by the concepts and principles disclosed herein, will be readilycapable of generating such software instructions and programs and ICswith minimal experimentation. Therefore, in the interest of brevity andminimizing any risk of obscuring the principles and concepts accordingto the present invention, further discussion of such software and ICs,if any, will be limited to the essentials with respect to the principlesand concepts of the various embodiments.

Referring now to FIG. 1, there is depicted, in a simplified andrepresentative form, a high-level block diagram of luminaire 100,connected in a constant wattage isolated (CWI) configuration, inaccordance with one or more embodiments. Luminaire 100 includesluminaire housing 102 for enclosing and supporting, lamp 104, ballastcircuit 106, and controller 114. Lamp 104 can be a high intensitydischarge (HID) lamp, such as, for example, a metal halide lamp, amercury vapor lamp, or a high-pressure sodium lamp. Light is generatedin an HID lamp by an arc which is established between two electrodes ina gas-filled tube. The arc causes a metallic vapor to produce a radiantenergy.

HID lamps have special electrical requirements that must be supplied bya ballast, such as ballast circuit 106, which is specifically designedfor the type of lamp, the ballast and ballast configuration, and theoperating wattage. The ballast provides system stability by limiting thecurrent that can be drawn through the HID lamp. Ballasts use inductiveand capacitive components because they impede alternating current withlittle power consumption. Thus, ballast circuit 106 includes transformer108 (the inductive component) and multi-tap capacitor 110 (thecapacitive component). In one embodiment, ballast circuit 106 can beimplemented with a 150 watt (W) ballast, such as ballast model # 71A8188manufactured and sold by Advance Transformer, located in Rosemont, Ill.

Exciter 112, which can also be referred to as an igniter, is a circuitfor providing a voltage to break down the gas between the electrodes oflamp 104 and initiate starting. For example, in one embodiment using a150 W ballast, exciter 112 can be implemented with igniter model #L1551J, manufactured and sold by Advance Transformer, located inRosemont, Ill.

Multi-tap capacitor 110, which is described more completely below,provides a selectable capacitance value in ballast circuit 106 in orderto adjust the intensity of lamp 104, and to control the power consumedby lamp 104, while maintaining the manufacturer's requirements forcapacitance in the ballast circuit, and for power within the circuit.The capacitance value of multi-tap capacitor 110 can be selected, orvariably controlled, by controller 114, which is coupled to multi-tapcapacitor 110 through wire (or wires) 308.

Power for luminaire 100 is received by power wires 116, where, in oneembodiment, the power is supplied from a typical alternating currentsource in a range of 110 volts, alternating current (VAC) to 480 VAC. Inthe embodiment shown, one of the power supply wires 116 passes throughcontroller 114 so that luminaire 100 can be switched on and off by aswitch in controller 114 (not shown).

Controller 114 is used to turn luminaire 100 on and off, and to controlthe brightness of lamp 104 by selecting one of a plurality of lumenlevels between a dimmest mode of operation and a brightest mode ofoperation, where the lumen level is selected in response to a triggeringevent.

Controller 114 includes processor 118, which is coupled to memory 120,and a plurality of switches 122. Processor 118 can perform many of thefunctions and operations that occur within controller 114 by executingprogram code (e.g., software) and using data stored in memory 120. Inone embodiment, processor 118 can include one or more microprocessors,microcontrollers, or digital signal processors, which are each wellknown and readily available. For example, in one embodiment processor118 can be implemented with the microcontroller manufactured and soldunder part number ATMEGA128L-8A1 by ATMEL Corporation, in San Jose,Calif.

Processor 118 can be coupled to memory 120 through interface 124, which,in one embodiment, is configured to transfer data and program code forprocessing and execution in processor 118. In some embodiments,processor 118 can also include internal memory, which can be used forstoring program code and/or data.

Memory 120 can be implemented using some combination of generally knownmemory technology, such as RAM, ROM, EPROM, magnetic memory, opticalmemory, and the like.

Memory 120 can include program code 126 and data storage 128, which canbe individually or collectively used to execute various algorithms,processes, and methods within processor 118 and luminaire 100. Forexample, program code 126 can include program code for processes andalgorithms that implement lumen change trigger detector 130, lumen leveladjuster 132, network interface 134, sensor compensator 136, and errordetector 137.

As will be described in greater detail below, lumen change triggerdetector 130 can be used to detect a triggering event, or thresholdcrossing (e.g., a monitored value exceeding or falling below apredetermined value), or a scheduled time, for changing the lumen outputof luminaire 100; lumen level adjuster 132 can be used for adjusting, orfine tuning, a lumen output of lamp 104 so that it more preciselymatches the lumen level called for in response to a correspondingtrigger; network interface 134 can be used to communicate data andcommands with other networked devices; sensor compensator 136 can beused to compensate sensor readings in response to environmentalconditions; and error detector 137 can be used to detect and reporterrors in the operation of luminaire 100.

Data storage 128 can be used to store data related to an operatingschedule, data related to operating in response to triggering events,and data logged to record various parameters of operation of luminaire100. Data storage 128 can include switch setting data 138, lumen levelschedule 140, log files 142, and photometric profiles 143, and sensorprofile data 144.

As will be described in greater detail below, switch setting data 138relates to the setting of switches 122 for a particular lumen outputlevel; lumen level schedule 140 is data that relates to scheduling aparticular lumen level output for a particular time of day; log files142 is data that relates to recording parameters of operation;photometric profiles 143 is historical data measurements thatcharacterizes luminaire operation under particular conditions; andsensor profile data 144 is data that relates to characterizing sensoroperation under various environmental conditions.

While much of the functionality of controller 114 can, in someembodiments, be attributed to software instructions as executed byprocessor 118, it will be appreciated that many of these operations canalso be performed by hardware, or some combination of software andhardware. Additionally, it will be appreciated by those of ordinaryskill that a multiplicity of other functions or operations, which arenot specifically shown, can be performed in a typical controller device,and that various of those can be implemented, at least in part, with theprocessor(s) and various software instructions, etc.

Switches 122 includes a plurality of individual switches, or switchingelements, 146, which each have a first switch terminal 148 coupled toone “tap” capacitor (described more completely below) inside the housingof multi-tap capacitor 110. A second switch terminal 150 of each switch146 is coupled together to a common wire. Switches 122 are coupled toprocessor 118 by interface 152, which interface can carry data toconfigure, or selectively open and close switches 148. By selectivelyopening and closing switches 148 various capacitance values can beproduced in multi-tap capacitor 110.

In one embodiment, switches 122 can be electronic switches, which useelectrical components instead of moving parts. For example, switches 122can be implemented with electronic switches sold under part numberQ6006DH3 by Teccor of Fort Worth, Tex. Ideally, switches 122 shouldtolerate to changes in temperature and voltage over time. In analternative embodiment, other types of switches can be used in place ofthe electronic switches. For example, relays can be used. Althoughelectronic switches can switch quickly, it should be noted that it willtake time for lamp 104 to either heat up or cool down in response to achange of voltage in ballast circuit 106, and until the temperaturestabilizes a change in lamp output will not be fully in effect.

Controller 114 can also include sensor interface 154 coupled toprocessor 118 by data interface 155. Sensor interface 154 can be used toobtain and convert data from various sensors. For example, sensorinterface 154 can be coupled to daylight sensor 156, activity sensor158, and lumen level sensor 160, which are all described in greaterdetail below. If the sensors output an analog voltage level, sensorinterface 154 can be used to convert analog data to digital data, whichcan then be read and used by processor 118. Additionally, if sensors arenonlinear, sensor interface 154 can be used to normalize sensorreadings. If sensor readings tend to vary with ambient temperature,sensor interface 154 can be used to compensate sensor readings inresponse to the sensor temperature. In other embodiments suchnormalizing and compensating can be done by processor 118.

Controller 114 can also include transceiver 162 coupled to processor 118by data interface 163. Transceiver 162 can be coupled to antenna 164 forwirelessly communicating with other network devices, or controllers, ordata storage devices. For example, transceiver 162 can be used toreceive commands or messages that turn luminaire 100 on, or off, or to aparticular lumen level. Transceiver 162 can also be used to receivecontrol data for storing in lumen level schedule 140, or data forstoring in switch setting data 138, or other similar data for storing indata storage 128. Transceiver 162 can communicate data wirelessly usingradio frequency signals, infrared signals, or other wireless datatransmission techniques, or transceiver 162 can communicate data via awire, such as power wires 116 using power line carrier datatransmissions, or other wireline transmission techniques. In someembodiments, transceiver 162 can be separate from controller 114 whilestill sharing an interface with controller 114, wherein transceiver 162is not in a common housing with controller 114.

Transceiver 162 can also be used to send data from data storage 128. Forexample, in one embodiment, data such as log files 142, which canrepresent a time of operation at a particular lumen level and powerconsumption level, can be sent from data storage 128. Data regardingtimes and power consumption levels can be used for more accurate billingbecause data representing electricity actually used can be recorded byluminaire 100. Data in log files 142 that indicates a problem orerroneous operation can also be sent by transceiver 162.

With reference now to FIG. 2, there is depicted, in a simplified andrepresentative form, a high-level block diagram of luminaire 200, whichis similar to luminaire 100 except that it is connected in a constantwattage autotransformer (CWA) configuration, in accordance with one ormore embodiments. As shown, luminaire 200 includes housing 102 forenclosing and supporting lamp 104, ballast 202, and controller 114. Notethat ballast 202 is connected in a CWA configuration using autotransformer 204. Multi-tap capacitor 110 is in a series circuit with asecondary side of transformer 202, and with lamp 104. As described abovewith referenced FIG. 1, day light sensor 156, activity sensor 158, andlumen level sensor 160 are each coupled to controller 114. Antenna 164may also be coupled to controller 114 for receiving or transmittingdata.

Because the primary side of the ballast is not completely isolated fromthe secondary side in the CWA configuration, the CWI configuration ofFIG. 1 is preferred in some areas (e.g., cities, states, or countries).

Turning now to FIG. 3, there is depicted a perspective view of multi-tapcapacitor 110, which is also shown in FIGS. 1 and 2, and in schematicform in FIG. 4. As illustrated, multi-tap capacitor 110 has a housing302 and connector lugs 304 and 306. Connector lugs 304 and 306 aresupported by housing 302, and they are selectably connectable bycontroller 114 to a plurality of capacitors inside housing 302, whichcapacitors are described more completely with reference to FIG. 4,below. Connector lugs 304 and 306 are accessible from the exterior ofhousing 302, and are configured to receive spade connectors that areattached to wires, which are coupled to either lamp 104, or transformer108 or 202, or other components in the ballast circuit in order to placemulti-tap capacitor in the ballast circuit.

Multi-tap capacitor 110 can also include wire 308 that passes throughhousing 302. Connector 310 is located at one end of wire 308 forconnecting to controller 114. The other end of wire 308 is connectedinternally to one or more capacitors, as described more completely belowwith reference to FIG. 4. In one embodiment, connector 310 includes aplurality of connector pins 312, wherein each pin is located inside oneof the openings in connector 310. Wire 308 together with connector 310may be referred to as a wiring harness. This wiring harness can connectto a plug on controller 114, or it can connect to another complimentarywiring harness coupled to controller 114.

The size and shape of multi-tap capacitor 110, and connector lugs 304and 306, are selected so that multi-tap capacitor 110 can easily replacea capacitor typically used in a luminaire. Such capacitor replacementcan be part of retrofitting a conventional, non-adjustable luminairewith multi-tap capacitor 110 and controller 114 in order to create aluminaire that can be monitored and controlled, in terms of brightnessand power consumption, in a manner similar to that of luminaire 100.

Referring now to FIG. 4, there is depicted a schematic circuit diagramof multi-tap capacitor 110 (see FIGS. 1, 2, and 3) in accordance withone or more embodiments. As shown, multi-tap capacitor includes housing302, which, in a preferred embodiment, is a can made of metal or someother durable and resilient material. The shape, size, and material ofhousing 302 are, in one embodiment, typical of capacitors used in HIDballast circuits.

Coupled to housing 302 are terminals 304 and 306 for connecting to themulti-tap capacitance within housing 302. In one embodiment, terminals304 and 306 can be connector lugs, which are commonly used on capacitorsin HID ballast circuits.

Inside housing 302 there is a plurality of capacitors, wherein eachcapacitor is, in a preferred embodiment, coupled via wires 308 to aconnector pin (e.g., 402, 404, 406, 408, 410, 412, 414, and 416) inmulti-pin connector 310. In a preferred embodiment, multi-tap capacitor110 includes base capacitor 418 integrated with a plurality of tapcapacitors 420, 422, 424, 426, 428, and 430. In other embodiments,multi-tap capacitor 110 can have a plurality of tap capacitors that canbe selectively connected in parallel across lugs 304 and 306, butwithout a base capacitor permanently connected across lugs 304 and 306.Multi-tap capacitor 110 can also include resistor 432 connected inparallel with base capacitor 418 to discharge base capacitor 418 so thatit will not hold a charge and become a shock hazard.

The ballast type (i.e., CWA, CWI) and the lamp wattage are variablesthat determine the capacitance values within multi-tap capacitor 110 inballast circuit 106 and 202. Thus, the capacitor values within multi-tapcapacitor 110 depend upon the manufacturer of ballast transformer (e.g.,108 and 204) and lamp 104, and the rated wattages of each. Lampmanufacturers typically provide inductance and capacitance values andother parameters for selecting ballast circuit components. One of theparameters specified is the total capacitance required for fullbrightness, or full power, operation of the ballast circuit.

The capacitance value of base capacitor 418 (which can be noted asC_(base)) is preferably selected to operate luminaire 100 in a minimumbrightness mode, which mode consumes the least power (e.g., typicallyabout 50% of rated maximum power, depending upon the lamp manufacturer),and outputs the lowest lumen level. In order to determine thecapacitance value for operating at 50% power, or minimum brightness, theballast type and wattage is noted, and the ballast capacitor value isdetermined by reading tables on the manufacturer's datasheet. An exampleof data found in a manufacturer's datasheet is shown in Table 1, below:

TABLE 1 Example Data Sheet from Ballast Manufacturer Lamp Total BallastWattage Capacitance Type (Watts) Required (μF) CWA 150 55 CWA 250 35 CWA400 55 CWI 150 52 CWI 250 28

The capacitance value needed to operate luminaire 100 in a maximumbrightness mode (which value can be noted as C_(max)) can be used toselect the capacitance values of tap capacitors 420, 422, 424, 426, 428,and 430. For example, a capacitance value that can be added to basecapacitance 418 to operate luminaire 100 in a maximum brightness modespecified by the manufacturer (which value can be noted as C_(tap) _(—)_(tot)) is equal to the value of all tap capacitors added in parallel.The difference between C_(base) and C_(tap) _(—) _(tot) is the amount ofcapacitance available to use as multilevel power control, and is themagnitude of the range of variance of capacitor values in multi-tapcapacitor 110. The difference between C_(max) and C_(base) is C_(tap)_(—) _(tot).

If there are (t) number of tap capacitors, then each tap capacitor canhave a value (C_(x)) determined by the formula:

$C_{x} = {{\frac{C_{tap\_ tot}\left( 2^{2 - x} \right)}{2^{t} - 1}\mspace{14mu}{where}\mspace{14mu} x} = {1\mspace{14mu}{to}\mspace{14mu}{t.}}}$

The number of tap capacitors t can be determined by the desired numberof lumen adjustment levels, or the desired number of equally distributedsteps in multi-tap capacitance value between C_(base) and C_(max). Forexample, if (a) number of adjustment levels are desired, then the numberof tap capacitors, t, can be computed by the formula:t=log₂ a

For example, if 64 levels of adjustment are desired (e.g., a.=64), thenumber of tap capacitors t is equal to 6, as shown by the equation:t=log₂ 64=6

Table 2 below shows examples of base 418 and tap capacitor (420, 422,424, 426, 428, and 430) values that can be used to provide 64 selectablevalues of multi-tap capacitor 110 ranging from C_(base) to C_(max). Theexamples are for different ballast types (e.g. CWA and CWI), anddifferent lamp wattages. As can be seen, multi-tap capacitor 110 ispreferably designed based upon the ballast type and the manufacturer'srecommended minimum (e.g., C_(base)) and maximum (e.g., C_(max))capacitance values for safely operating lamp 104.

TABLE 2 Base and Tap Capacitor Values for different wattages and ballasttypes Total Base Lamp Capacitance Capacitor Ballast Wattage Requiredvalue C_(tap) _(—) _(tot) Type (Watts) C_(max) (μF) C_(base) (μF) (μF)C₁ C₂ C₃ C₄ C₅ C₆ CWA 150 55 40 15 7.62 3.81 1.9 0.95 0.48 0.24 CWA 25035 28 7 3.56 1.78 0.89 0.44 0.22 0.11 CWA 400 55 40 15 7.62 3.81 1.90.95 0.48 0.24 CWI 150 52 40 12 6.1 3.05 1.52 0.76 0.38 0.19 CWI 250 2821 7 3.56 1.78 0.89 0.44 0.22 0.11

Note that in one embodiment the values of the tap capacitors form ageometric progression with a common ratio of 1/2. These tap capacitorscan be switched in sequential combinations, similar to a sequence ofbinary numbers, to produce a near-continuously varying capacitance froma lowest value, equal to base capacitance 418 (e.g., C_(base)), to thehighest value, equal to the base capacitance plus C_(tap) _(—) _(tot)(i.e., all tap capacitors added in parallel), where a resolution of suchvarying capacitance is equal to the smallest tap capacitance value.

In one embodiment, base capacitor 418 is permanently connected acrossterminal lugs 304 and 306 so that the minimum multi-tap capacitanceappearing across lugs 304 and 306 is the base capacitance value, whichis the minimum value for lamp 104 operation. This prevents luminaire 100from losing an arc and having to restart.

Turning now to the operation of luminaire 100 (or 200), FIG. 5 depicts ahigh-level flowchart 500 having exemplary processes executed by aluminaire and luminaire controller, such as luminaire 100 luminairecontroller 114, or executed by another similar apparatus, in accordancewith one or more embodiments. As illustrated, the process begins at 502,and thereafter passes to 504 wherein the process sets switches toproduce a capacitance in a multi-tap capacitor that corresponds to aninitial lumen level. The initial lumen level can be, for example,turning luminaire 100 from off to on with at a specified lumen level. Inone embodiment, setting the switches can be implemented with processor118 coupled to switches 122 through interface 152, as shown in FIG. 1.Processor 118 can send digital control signals to solid state electronicswitches to selectively put switches 146 into an open circuit state(e.g., high impedance state) or a closed circuit state (e.g., conductivestate). As switches 146 are set to the conductive state they connectcorresponding tap capacitors in parallel wherein the values of the tapcapacitors are added together to produce the multi-tap capacitance,which can be measured across terminals 304 and 306

Next, the process determines whether a lumen change trigger hasoccurred, as shown at block 506. A lumen change trigger is apredetermined condition that initiates a change in lumen output of theluminaire that is needed or desired. For example, a lumen change triggercan be a time of day, which is recorded in a schedule, such as lumenlevel schedule 140, or another similar table or database. In anotherembodiment, a lumen change trigger can be detecting an activity levelthat crosses above or below a threshold. Such an activity level can bedetected by a sensor measuring pedestrian or vehicle traffic along aroadway or at an intersection. Activity levels can be measured or sensedwith sensor 158, which sensor can be an infrared, radar, or sonar motiondetector, a street crosswalk button, a vehicle sensor in the pavement ofthe roadway, a camera adapted to detect vehicles or person, or the like.

Another lumen change trigger can be a particular weather condition, suchas rain, snow, fog, or other weather condition in which an increased ordecreased level of light is useful or desired. Environmental or weatherconditions can effect the apparent illumination from luminaires. Duringfog, rain, or snow, it is often desirable to increase the illuminationfrom the overhead luminaires in order to improve visibility at groundlevel.

In another embodiment, a lumen level change trigger can be a message orcommand received by transceiver 160, or another similar data receiver.Such a message can be a command to turn on or turn off, or a command tochange to a particular lumen output level. Such commands can be receivedfrom a central controller either directly or through a network. Commandscan be received as a relayed message from another luminaire 100, whereinsuch luminaires work together as part of a mesh data communicationnetwork, where messages are relayed from luminaire to luminaire.Transceiver 160 can be any one of various known data receivers (ortransceivers if transmission from luminaire 100 is needed), such as, forexample, a radio frequency receiver, an infrared data receiver, a lightpulse receiver, or the like.

Other embodiments can receive a lumen level trigger from signalstransmitted from an emergency vehicle. For example, the signal on anemergency vehicle that turns intersection lights green for ambulancesand fire trucks (e.g., a strobe light set to flash at a predeterminedfrequency, which can be received by a light pulse receiver) can also beused as a lumen level trigger suitable for a high speed response to anemergency. Other emergency signals can also be a lumen level trigger.For example, a building alarm can send out a message or signal that canbe received by luminaire 100. In response to such an alarm, luminaire100 can be triggered to increase lumen output to a maximum lumen level,which can help emergency personnel handle the situation that caused thealarm.

In yet another embodiment, a lumen level trigger can be a command sent,perhaps from a power company, instructing devices to shed or reduce anelectrical load in order to ease the demand for power. For example, inresponse to demand for electricity exceeding a threshold, the powercompany can send a signal that requests selected devices to reduce theirdemand for power, and enter an energy saving mode. When luminaire 100receives such a request, it can reduce the lumen output to reduceelectricity consumption.

FIG. 8 depicts an example of a lumen level schedule 140 in the form of atable 800 that contains trigger events 802 and corresponding lumenlevels 804. As discussed above, trigger events 802 can be a time of day,or the presence of an emergency vehicle (e.g., the detection of a signalfrom an emergency vehicle), or the reception of a load shedding command,or the like. Associated with these trigger events 802 is a lumen level804, which is a light output level that is selected or scheduled to beoutput by luminaire 100 when the trigger event occurs. In oneembodiment, there can be several tables or schedules similar to table800, wherein each schedule runs under particular circumstances. Forexample, one table 800 can be for weekdays, while another table is forweekends. There can be schedules for special events, and there can beschedules for different parts of the year.

After detecting the lumen level trigger, the process determines a newlumen level in response to the detected trigger, as shown at 508. In oneembodiment, the process can look up a new lumen level in a schedule ordata table (e.g., table 800 in FIG. 8), wherein the new lumen level 804corresponds to the detected trigger 802. For example, in one embodiment,lumen change trigger detector 130 can detect a time of day having ascheduled lumen change, and in response to the time of day, the processcan look up a new lumen level in schedule 800 that is associated withthe detected time of day.

After looking up new lumen level, the process determines switch settingsthat correspond to the new lumen level, as illustrated at 510. Theswitch settings are for configuring switches 148 to produce a multi-tapcapacitance in multi-tap capacitor 110 having a value selected tooperate luminaire 100 at the new lumen output. In one embodiment, themaximum multi-tap capacitance can be produced in multi-tap capacitor 110by setting all switches 146 to the conductive state, thereby connectingall tap capacitors (420, 422, 424, 426, 428, and 430) in parallel withbase capacitor 418. A minimum multi-tap capacitance can be produced bysetting all switches 146 to the open circuit state. Various other lumenoutput levels can be set by using other combinations of opened andclosed switches. With the embodiment of multi-tap capacitor 110 shown inFIG.4, which has six tap capacitors, 64 different multi-tap capacitancescan be produced using all possible open and closed settings for the 6corresponding switches 148 in controller 114.

Next, the process configures the switches to produce the multi-tapcapacitance value in the multi-tap capacitor, where the multi-tapcapacitance value corresponds to the new lumen level, as illustrated at512. In one embodiment, this can be implemented by sending signals fromprocessor 118 to switches 122 via interface 152, wherein the signalscontrol individual switches 146, selectively placing them in the opencircuit or closed circuit state to create parallel connections ofselected tap capacitors (420, 422, 424, 426, 428, and 430) connected inparallel with base capacitor 418 within multi-tap capacitor 110. Thus,in response to the controller's selection or enabling commands,secondary voltage is output from multi-tap capacitor 110 to the ballastcircuit.

After configuring the switches to produce the next capacitance value inmulti-tap capacitor 110, the process measures a lumen level output bylamp 104, as depicted at 514. In one embodiment, this step isimplemented by reading from sensor interface 154 a value output by lumenlevel sensor 160.

In some embodiments, the accuracy of lumen level sensor 160 can beimproved if the process also reads the current operating conditions thatcan affect the output of lumen level sensor 160, such as the temperatureof lumen level sensor 160. Then the process can compensate for theaffects of temperature and other operating conditions by referring totables of data or equations, and applying appropriate compensationfactors to correct or compensate the reading from lumen level sensor160. In one embodiment, lumen level sensor 160 can have a portion of thesensor (i.e., a portion integral to the sensor) that measures thetemperature of the lumen sensor so that the lumen sensor output can becompensated using sensor profile data 144 that describes the operationof the sensor over various environmental conditions.

After measuring the lumen level output, the process compares themeasured lumen level output to the new lumen level, as depicted at 516.This comparison produces an error value, or a difference, between themeasured lumen level and the new lumen level.

One reason for comparing the measured lumen level output to the newlumen level value is that reducing the system input power may notproportionally reduce the lumen output. Therefore, when a lamp isadjusted, the reduction in lumen output can be greater than thereduction in the system input power, which means that the efficiency candecrease as the lamp is adjusted.

Because HID lamps may not immediately adjust the light output when themulti-tap capacitance value is changed, in some embodiments there can bea delay between configuring the switches in 512 and measuring the lumenlevel output in 514. When some systems are dimmed from full power tominimum power, approximately half of the total change in the lightoutput occurs within the first few seconds. Then it can take from 3 to10 additional minutes for the light to stabilize. In other instances,depending upon the characteristics of the particular ballast-lampcombination, the lamps can respond instantly to small changes in inputpower.

Some manufacturers claim that operating a halide or mercury vapor lampin a dimmed mode can actually increase the lamp lumen depreciation ofmetal, which in turn produces undesirable optical effects, such asflickering or distortions. A reduction of power to these types of lampscauses the arc tube to blacken due to electrode sputtering, which canchange the lumen output over time. To help limit this effect, lampmanufacturers recommend that such lamps not be dimmed below 50% of ratedpower. Thus, in general, a 50% power level must be maintained within theballast-lamp circuit to provide satisfactory lamp operation.

After determining the difference between the measured lumen level outputand the new lumen level, the process determines whether a lumenadjustment is necessary, as shown at 518. A lumen level adjustment canbe necessary if the difference exceeds a predetermined value.

If the lumen adjustment is necessary, the process passes to block 520,where the process reconfigures the switches to change the multi-tapcapacitance to compensate for the difference between the measured lumenlevel output and the new lumen level. In one embodiment, this step canbe implemented by changing the switch settings to either raise or lowerthe multi-tap capacitance to reduce the error value. This step providesfeedback to controller 114 so that controller 114 can more accuratelycontrol the lumen level output of luminaire 100. Such feedback is neededbecause over time, the correlation of multi-tap capacitor values(selected by particular switch settings) to lumen output levels candrift as lamp 104 ages (e.g., as the inside of the lamp darkens with thebyproducts of arcing), or as temperature effects the operation ofluminaire 100.

After reconfiguring the switches, the process logs the compensatedswitch configuration, as shown at 522. In one embodiment, this step canbe implemented by changing switch setting data 138 (see FIG. 1) in atable or database that corresponds to the new lumen level. By changingthe data in switch setting data 138, luminaire 100 remains accurate foreach lumen level called for, or indicated by, the corresponding lumenchange trigger. Thus, luminaire 100 will not put out more light thanneeded, thereby wasting energy, nor will it put out less light thanneeded, causing unsafe conditions or difficulties in seeing.

Briefly referring to FIG. 6, table 600 shows an example of data that canbe stored in switch setting data 138 in FIG. 1. As illustrated, column602 lists all possible lumen levels that can be output by luminaire 100.Such lumen levels can be listed in foot candle units, or ADC valuesmeasured by a lamp sensor during a luminance characterization processspecific to this particular ballast, igniter, and lamp combination.Column 604 can list dimming levels that correspond to the lumen levelsin 602. Data representing switch settings can be stored in column 606.In the embodiment shown, switch settings 606 are stored as Boolean datathat corresponds to conducting (e.g., on) and non-conducting (e.g., off)switch elements 146. Switch settings 606 can be the original switchsettings programmed into luminaire 100. After switch settings have beenadjusted to compensate for the difference between the measured lumenlevel output and the new lumen level, adjusted switch settings can bestored in column 608 so that the next time luminaire 100 is set to aparticular lumen level 602, the adjusted switch setting 608 can be usedwith the expectation that it is more accurate.

Referring back to FIG. 5, after the compensated switch setting is loggedat 522, the process logs the time and data that represents the switchsettings for the new lumen level, as illustrated at 524. In oneembodiment, this process can be implemented by recording the time andthe switch setting in log files 142. Note that the time and switchsetting data can be used to calculate the energy used by luminaire 100,if there is additional data available to correlate switch settings to arate of power consumption. This power usage calculation can be done by acentral system control computer using data collected from log file 142in one or more networked luminaires 100. Thus, data stored in the logfiles 142 can be used to bill the owner of luminaire 100 for electricitythat is actually used rather than guessing the amount of the electricbill based upon the number of luminaires. Because luminaire 100 canrecord data related to its energy consumption, there is a monetaryincentive to install such power control systems, in addition to the factthat energy is saved.

An example of a log file 142 is shown in FIG. 7. As shown, table 700includes column 702 for storing a time and date. The date can berepresented as a month, day, and year. The time can be representedaccording to a 24 hour clock, with hours, minutes, and seconds. Ifcontroller 114 is expected to record invents that can take place in lessthan a second, then the time can include fractions of a second asnecessary. Table 700 also includes column 704 for storing a descriptionof the event or status condition being logged. Examples of events orstatus that can be logged are: setting switches in response to aparticular triggering event, the compensation of switch settings for aparticular lumen level, an error conditions such as a lamp failure, lampcycling, and other similar events and status.

Portions of the above described functions and structures can beimplemented in one or more integrated circuits. For example, many of thefunctions can be implemented in the signal and data processing circuitrythat is suggested by the block diagram shown in FIG. 1. The program codesuggested by the algorithm and processes of the flowchart of FIG. 5 canbe stored in program code 126, which is shown in FIG. 1.

The processes, apparatus, and systems, discussed above, and theinventive principles thereof are intended to produce an improved, moreefficient, and more reliable luminaire. In general, the power andbrightness of a luminaire can be controlled by a power control circuitthat uses an integrated multiple-tap capacitor, under the direction of acontroller. The multi-tap capacitor can be substituted for aconventional ballast capacitor in a conventional ballast circuit of aluminaire fixture. Furthermore, such processes, apparatus, and systems,discussed above, are suitable for use in conjunction with digital orelectronic ballasts for HID luminaires.

In order to take full advantage of the features and capabilities ofluminaire 100, luminaire 100 can be an integral part of a larger systemfor monitoring and controlling large lighting systems (e.g., municipallighting systems) that extend over many square miles and include manythousands of luminaires. Such lighting management systems can sendoperating control data to the thousands of luminaires to individuallycontrol the luminaire according to a customized schedule. The lightingmanagement system can also collect data representing power consumed byeach of the thousands of luminaires, thereby saving electricity, andcollecting accounting data that can provide the basis for reducedelectrical billing.

An important aspect of the lighting management system is the creationand use of an accurate database that characterizes the lumen outputlevels for each of the selectable multi-tap capacitor 110 values whenthe multi-tap capacitor is combined in luminaire 100 with a particularballast 108, having a ballast type (e.g., CWI 106, or CWA 202), aballast wattage, and in combination with a particular lamp, that ismanufactured by a particular company, and uses a particular technology(e.g., HPS, MV), in a particular wattage. The database generallyincludes power consumption and lumen output measurements for allselectable multi-tap capacitor 110 values for all practical combinationsof each major component in the lamp circuit.

Referring now to FIG. 9, there is depicted a portion of a databasecontaining luminance characterization profiles in accordance with one ormore embodiments. Luminance characterization profile 900 includes datarelated to the testing of multi-tap capacitor 110 using a particularballast and lamp combination. As shown, luminance characterizationprofile 900 includes a plurality of columns of data, which can includetime data 902 that shows the time that the measurements were made.

Column 904 (e.g., another field in the database) can contain luminancemeasurements of the output of lamp 104 when multi-tap capacitor 110 isset for a corresponding dimming level 906. Each dimming levelcorresponds to operating lamp 104 with a selected ballast capacitanceformed by a set of tap capacitors (420, 422, 424, 426, 428, and 430)connected in parallel with base capacitor 418. Luminance measurements904 can be made with a photometer, such as photometer 1108, which isdiscussed below with reference to FIG. 11.

Column 908 includes measurements of real power, measurement inkilowatts. Column 910 includes power factor measurements. Themeasurements in columns 908 and 910 can be made with a power meter, suchas power meter 1106, which is discussed below with reference to FIG. 11.

Turning briefly now to FIG. 11, there is depicted test station 1100 forcreating a luminance characterization profile 900 in accordance with oneor more embodiments. As s shown, test station 1100 can include testcontroller 1102, which is coupled to memory 1104, power meter 1106, andphotometer 1108. Multi-tap capacitor 110 is coupled to lamp 104 andballast transformer 108, which, in this example, is configured as a CWIballast.

Test controller 1102 can be implemented with a suitably programmedpersonal computer having appropriate interfaces for controlling andcommunicating with power meter 1106 and photometer 1108. In oneembodiment, memory 1104 can be contained within the “personal computer”test controller 1102. Interfaces with power meter 1106 and photometer1108 can be conventional computer data networking interfaces, such asIEEE 488, which is known as the Hewlett-Packard Instrument Bus (HP-IB),which is commonly used for connecting electronic test and measurementdevices to controllers such as computers.

In another embodiment, test controller 1102 can be controller 114 inluminaire 100 that is operating in a specially programmed mode, or in amode where it can be externally controlled by a personal computer toconduct luminance characterization profiles. Thus, when test controller1102 is implemented with controller 114, switches 122 can be theswitches in controller 114. With the “personal computer” test controller1102, switches 122 can be relays, manually controlled switches, orsolid-state electronic switching devices.

In one embodiment, power meter 1106 can be an ION® 7300 power meter fromPower Measurement based in Saanichton, BC Canada. Power meter 1106 canmeasure real and imaginary parts of the power supplied to ballasttransformer 108, so that measurements from power meter 1106 can includea real power measurement in kilowatts 908, and a power factormeasurement 910 in degrees.

With reference now to FIG. 10, there is depicted a high-level flowchartof the process of creating a luminance characterization profile 900 inaccordance with one or more embodiments. As illustrated, the processbegins at 1002, and thereafter passes to 1004 wherein the process enterstest description data, component description data, and parameter data toproperly document the luminance characterization profile, so that it maybe later recalled and used to develop lumen level schedules havingswitch configurations that accurately produce a lumen level output.

Next, the test circuit is connected, including connecting a ballasttransformer, a lamp, and a multi-tap capacitor in the configurationshown in FIG. 11. As shown in FIG. 11, multi-tap capacitor 110 isconnected in series with lamp 104, and in series with a secondary sideof ballast transformer 108, which is substantially similar to thecircuit shown and described with reference to FIG. 1 where luminaire 100has a CWI ballast configuration. Exciter 112 is also connected as shownin order to start lamp 104. Note that the test circuit connected at 1006can be connected in either the CWA ballast configuration 106, or the CWIballast configuration 202, depending upon which luminairecharacterization profile 900 is being created.

After connecting the test circuit, instruments are connected to the testcircuit, including a photometer and a power meter, as illustrated at1008. FIG. 11 shows that photometer 1108 is placed near lamp 104 inorder to measure the luminance output in foot-candles. In oneembodiment, the photometer and the lamp can be located in a controlledoptical chamber. FIG. 11 also shows that power meter 1106 is connectedat the alternating current input to ballast transformer 108.

At 1010 the process sets the switches coupled to multi-tap capacitor forthe first lumen level that will be measured. Thereafter, the processmeasures the luminaire output 904, which can be in units offoot-candles, as depicted at 1012. At 1014, the power input is measured(e.g., read from power meter 1106), with real power 908 measured inkilowatts, and a power factor 910 in degrees.

After reading the measurements, the process records the time, switchsetting (e.g., the dimming level 906), and the measured data 904, 908,and 910 in a record of luminaire characterization profile 900.

After recording the record, the process determines whether there is anext multi-tap capacitor switch setting that puts multi-tap capacitor110 in a configuration that has not been tested, as illustrated at 1020.If there are switch settings that have not been tested, the process setsthe switches to the next setting, as depicted at 1022. Thereafter, theprocess iteratively returns to 1012 to continue testing.

If, at 1020, all the switch settings have been tested, the process ofcreating luminaire characterization profile 900 is finished, and theprocess ends, as shown at 1024. Note that the process depicted in FIG.10 will be repeated many times in order to characterize the manycombinations of lamps, ballasts, etc.

The pseudo code listed below is an example of the number of times theprocess of FIG. 10 will be repeated to characterize the manycombinations of components that can be used in luminaire 100. Note thatthere are a number of different parameters that can be used incollecting luminaire characterization profiles to create a database thatincludes a number of luminaire characterization profiles 900 accordingto the process depicted in FIG. 10, or another similar process. Thepseudo code listed below represents iterative, nested loops that eachexecute the process depicted in FIG. 10.

For each BALLAST MANUFACTURER  For each MODEL OF BALLAST   For eachBALLAST TYPE    For each BALLAST WATTAGE     For each LAMP MANUFACTURER     For each LAMP TYPE (eg HPS, MV)       For each LAMP MODEL       For each LAMP FILAMENT TYPE (e.g. single or dual)         Foreach LAMP WATTAGE          Collect luminance characterization         profile ( see FIG. 10).         Endfor        Endfor      Endfor      Endfor     Endfor    Endfor   Endfor  Endfor Endfor

Thus, the process depicted in FIG. 10 can be repeated many times asrepresented by all the “nested loops” above in order to develop thedatabase that will help lighting designers incorporate a controlledmulti-tap capacitor 110 into a luminaire in order to adjust thebrightness of the luminaire to save energy and money. The processdepicted in FIG. 10 can be executed by an independent certification labto verify that the multi-tap capacitor design produces the stated outputvalues, and to produce a luminance characterization profile thatlighting engineers can use to prepare lighting schedules for variouslighting tasks. In some embodiments, luminaire 100 can guarantee a levelof light output based upon such a database of luminance characterizationprofiles, and supplemented by feedback adjustments of lumen outputlevels based upon field measurements within luminaire 100.

To create a record in the luminance characterization profile, it ishelpful to know the following information:

a) the Ballast Manufacturer, which is not necessarily the same entity asthe lamp manufacturer;

b) the Lamp Manufacturer, which is not necessarily the same entity asthe Ballast Manufacturer;

c) Ballast Manufacturer;

d) Model of Ballast: this is the manufacturer's model number.

e) Ballast Type: for HID applications, this is either CWA or CWI.

f) Ballast Wattage;

g) Lamp Manufacturer;

h) Lamp Type: lamps are manufactured containing different types of gases(e.g., HPS and MV are two of the most common);

i) Lamp Model;

j) Lamp Wattage; and

k) Lamp Filaments.

Once the database of luminance characterization profiles 900 has beencreated, it can be used to program a controller 114 that is installed ina new luminaire 100, or one that is being retrofitted into an olderluminaire. Such data can increase the accuracy of the correlation oflumen level output with dimming levels 906 or switch settings 606.Additionally, the database can be used when luminaires are repaired andnew ballasts or lamps are installed that are not exactly like theoriginal components. Thus, if a luminaire must have a different ballastinstalled, the database can be used to calibrate the luminaire for thedifferent ballast. This means that the database can help maintainaccurate lumen level outputs as the older luminaires are repaired withdifferent or newer parts.

This disclosure is intended to explain how to fashion and use variousembodiments in accordance with the invention, rather than to limit thetrue, intended, and fair scope and spirit thereof. The foregoingdescription is not intended to be exhaustive or to limit the inventionto the precise form disclosed. Modifications or variations are possiblein light of the above teachings. The embodiment(s) were chosen anddescribed to provide the best illustration of the principles of theinvention and its practical application, and to enable one of ordinaryskill in the art to utilize the invention in various embodiments andwith various modifications as are suited to the particular usecontemplated. All such modifications and variations are within the scopeof the invention as determined by the appended claims, as may be amendedduring the pendency of this application for patent, and all equivalentsthereof, when interpreted in accordance with the breadth to which theyare fairly, legally, and equitably entitled.

1. A system for luminance characterization of a luminaire comprising: aballast coil; a multi-tap capacitor connected in series with the ballastcoil, wherein the multi-tap capacitor has a plurality of tap capacitorsintegrated into a capacitor housing; a plurality of switches, whereineach switch is coupled to one of the plurality of tap capacitors forselectively coupling the tap capacitors together to produce a multi-tapcapacitance corresponding to a configuration of the plurality ofswitches; a lamp connected in series with the multi-tap capacitor andthe ballast coil; a photometer located to measure light intensity of thelamp and to produce a lumen output measurement; and a memory for storinga database having a plurality of lumen output measurements correspondingto each multi-tap capacitance, wherein each multi-tap capacitancecorresponds to one of a set of all configurations of the plurality ofswitches.
 2. The system for luminance characterization according toclaim 1 comprising a processor coupled to the photometer and the memoryfor reading the lumen output measurements and recording the lumen outputmeasurements in the database.
 3. The system for luminancecharacterization according to claim 1 comprising a power meter coupledto a power supply that is coupled to a power input of the ballast coilfor measuring power consumption of the luminaire.
 4. The system forluminance characterization according to claim 3 wherein the power metermeasures real power consumption and a power factor.
 5. The system forluminance characterization according to claim 1 wherein the plurality ofswitches is a plurality of electronic switching elements.
 6. The systemfor luminance characterization according to claim 1 wherein theplurality of switches is a plurality of relay switches.
 7. The systemfor luminance characterization according to claim 2 wherein theprocessor is coupled to the plurality of switches for configuring theswitches through all of the configurations of the plurality of switches.8. The system for luminance characterization according to claim 1wherein the multi-tap capacitor comprises a base capacitor integratedinto the capacitor housing, wherein the base capacitor has first andsecond terminals connected, respectively, to a first and a secondconnector lug, wherein each of the plurality of tap capacitors has afirst tap capacitor terminal and a second tap capacitor terminal,wherein the first terminal of the base capacitor and each of the firsttap capacitor terminals is connected, respectively, to a correspondingconnector pin in a multi-pin connector, and wherein the second tapcapacitor terminals are connected to the second terminal and the secondconnector lug, wherein the multi-tap capacitance is measured between thefirst and second connector lugs, and can be configured to be equal tothe base capacitor value plus values of one or more selected tapcapacitors connected in parallel with the base capacitor by theplurality of switches.
 9. The system for luminance characterizationaccording to claim 8 wherein the multi-tap capacitor has (t) number oftap capacitors, and wherein the t tap capacitors have a capacitancevalue (C_(x)) where$C_{x} = \frac{C_{tap\_ tot}\left( 2^{t - x} \right)}{2^{t} - 1}$ for xequal 1 to t, where C_(tap) _(—) _(tot) has a value equal to thedifference between a capacitance value for operating the luminaire at aminimum brightness and a capacitance value for operating the luminaireat a maximum brightness.
 10. The system for luminance characterizationaccording to claim 8 wherein the base capacitor has a capacitance valueselected to operate the luminaire in a minimum brightness mode.
 11. Amethod for luminance characterization of a luminaire comprising:providing a ballast coil; connecting a multi-tap capacitor in serieswith the ballast coil, wherein the multi-tap capacitor has a pluralityof tap capacitors integrated into a capacitor housing; coupling aplurality of switches to each one of the plurality of tap capacitors forselectively coupling the tap capacitors together to produce a multi-tapcapacitance corresponding to a configuration of the plurality ofswitches; connected a lamp in series with the multi-tap capacitor andthe ballast coil; locating a photometer to measure light intensity ofthe lamp and to produce a lumen output measurement; and storing adatabase in a memory, wherein the database has a plurality of lumenoutput measurements that correspond to each multi-tap capacitance,wherein each multi-tap capacitance corresponds to one of a set of allconfigurations of the plurality of switches.
 12. The method forluminance characterization of a luminaire according to claim 11 whereinthe storing a database in a memory comprises stepping throughconfigurations of the plurality of switches and storing the lumen outputmeasurements in response to each configuration of the plurality ofswitches.
 13. The method for luminance characterization of a luminaireaccording to claim 11 wherein connecting a multi-tap capacitor comprisesconnecting a multi-tap capacitor having a base capacitor integrated intothe capacitor housing, wherein the base capacitor has first and secondterminals connected, respectively, to a first and a second connectorlug, wherein each of the plurality of tap capacitors has a first tapcapacitor terminal and a second tap capacitor terminal, wherein thefirst terminal of the base capacitor and each of the first tap capacitorterminals is connected, respectively, to a corresponding connector pinin a multi-pin connector, and wherein the second tap capacitor terminalsare connected to the second terminal and the second connector lug,wherein the multi-tap capacitance is measured between the first andsecond connector lugs, and can be configured to be equal to the basecapacitor value plus values of one or more selected tap capacitorsconnected in parallel with the base capacitor by the plurality ofswitches.
 14. The method for luminance characterization of a luminaireaccording to claim 13 wherein the connecting a multi-tap capacitorcomprises connecting a multi-tap capacitor having (t) number of tapcapacitors, and wherein the t tap capacitors have a capacitance value(C_(x)) where$C_{x} = \frac{C_{tap\_ tot}\left( 2^{t - x} \right)}{2^{t} - 1}$ for xequal 1 to t, where C_(tap) _(—) _(tot) has a value equal to thedifference between a capacitance value for operating the luminaire at aminimum brightness and a capacitance value for operating the luminaireat a maximum brightness.
 15. The method for luminance characterizationof a luminaire according to claim 13 wherein the connecting a multi-tapcapacitor comprises connecting a multi-tap capacitor wherein the basecapacitor has a capacitance value selected to operate the luminaire in aminimum brightness mode.
 16. The method for luminance characterizationof a luminaire according to claim 11 comprises: connecting a power meterto a power source of the ballast coil; measuring a power consumption ofthe luminaire for each configuration of the switches; and storing thepower consumption in the database.
 17. The method for luminancecharacterization of a luminaire according to claim 16 wherein themeasuring a power consumption comprises: measuring a real powerconsumption and a power factor; and storing the real power consumptionand the power factor in the database.
 18. A luminaire and correspondingdata set of luminance characterization information the luminairecomprising: a ballast coil; a multi-tap capacitor connected in serieswith the ballast coil, wherein the multi-tap capacitor has a pluralityof tap capacitors integrated into a capacitor housing; a plurality ofswitches, wherein each switch is coupled to one of the plurality of tapcapacitors for selectively coupling the tap capacitors together toproduce a multi-tap capacitance corresponding to a configuration of theplurality of switches; and a lamp connected in series with the multi-tapcapacitor and the ballast coil; and the data set comprising recordspertaining to lumen output measurements of the luminaire, wherein thedata set has a plurality of records relating the lumen outputmeasurements to each multi-tap capacitance, wherein each multi-tapcapacitance corresponds to one of a set of configurations of theplurality of switches.
 19. The luminaire and corresponding data set ofclaim 18 wherein the multi-tap capacitor comprises a base capacitorintegrated into the capacitor housing, wherein the base capacitor hasfirst and second terminals connected, respectively, to a first and asecond connector lug, wherein each of the plurality of tap capacitorshas a first tap capacitor terminal and a second tap capacitor terminal,wherein the first terminal of the base capacitor and each of the firsttap capacitor terminals is connected, respectively, to a correspondingconnector pin in a multi-pin connector, and wherein the second tapcapacitor terminals are connected to the second terminal and the secondconnector lug. wherein the multi-tap capacitance is measured between thefirst and second connector lugs, and can be configured to be equal tothe base capacitor value plus values of one or more selected tapcapacitors connected in parallel with the base capacitor by theplurality of switches.
 20. The luminaire and corresponding data set ofclaim 19 wherein the multi-tap capacitor has (t) number of tapcapacitors, and wherein the t tap capacitors have a capacitance value(C_(x)) where$C_{x} = \frac{\;{C_{\;{tap\_ tot}}\;\left( \; 2^{t - x} \right)}}{\;{2^{t} - 1}}$for x equal 1 to t, where C_(tap) _(—) _(tot) has a value equal to thedifference between a capacitance value for operating the luminaire at aminimum brightness and a capacitance value for operating the luminaireat a maximum brightness.